1. Field of the Invention
The present invention relates to an electric steering lock device (ESL) for electrically locking the rotation of a steering wheel when a vehicle is parked.
2. Description of the Related Art
Recently, there is a vehicle equipped with an electric steering lock device for electrically locking the rotation of a steering wheel during the parking for the purpose of preventing theft.
As an example of such an electric steering lock device, Japanese Patent Application Publication No. 2006-036110 has proposed a device including: a shaft which includes a male threaded portion and which is rotationally driven by an electric motor; a lock stopper which includes a female threaded portion threadedly engaging with the male threaded portion of the shaft and which advances and retreats in response to the rotation of the shaft; and a lock bar which is coupled to the lock stopper via a pin and which is engageable with and disengageable from a recessed groove of a steering shaft.
However, in the electric steering lock device proposed in Japanese Patent Application Publication No. 2006-036110, if the pin breaks due to deterioration over time, the movement of the lock bar cannot be restricted. Hence, when some kind of load is applied to the lock bar and the lock bar thereby moves to a locked position, the steering shaft may be unintentionally locked.